U.S. shares advanced, with the Standard & Poor's 500 Index reversing the earlier declines, after the Atlanta Fed's President Dennis Lockhart said the central bank is committed to its stimulus. The S&P 500 advanced 0.6% to 1,640.42 as of 4 p.m. in New York, while the Dow gained 138.46 points to 15,254.03. The S&P 500 dropped 1.1% previous week.